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Confused on Gravity

  1. Nov 29, 2009 #1
    I'm confused! Gravity is the weakest force...right. How is it possible to hypothesize that a black hole scenario of gravitation being stong enough that nothing else can escape?
     
  2. jcsd
  3. Nov 29, 2009 #2

    DaveC426913

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    Because gravity is
    1] cumulative (Every single particle pulls on every other particle.)
    2] infinite in extent (the other forces act over extremely short distances.)
     
  4. Nov 29, 2009 #3
    thankyou!
    So as it accumulates it becomes the strongest force.
     
  5. Dec 1, 2009 #4
    This is correct. Plus, there is a lot of space between the molecules that make up our planet, just as there is a lot of space that make up our sun.
    As the gravitational body aquires more mass, it exerts a greater gravitational field. Ultimately, the increase in gravity condenses the molecules that make up the earth and sun to such an extent that there is no space left in between the molecules that make up the earth and sun. A very massive body + no room in between the molecules of the massive body = a black hole that excerts the strongest known force.
     
  6. Dec 1, 2009 #5
    Hi there,

    By saying the weakest force, you might want to precise. Gravity is the weakest of the four fundamental interaction, but for short distance only. By short distance, I mean from a few pm up to a few thousands (maybe millions km).

    The greater the distance is, the weaker the other three interactions become. Therefore, on very large scale, only the gravitational interaction is left to do the work.

    Cheers
     
  7. Dec 1, 2009 #6

    Vanadium 50

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    That's not true - or rather, it's true but misleading. Both EM and gravity fall off as 1/r2. The other two fall off faster. The reason that gravity wins out over large distances is that it is always attractive, whereas electromagnetism is sometimes attractive and sometimes repulsive.
     
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